首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1273篇
  免费   78篇
  国内免费   8篇
电工技术   16篇
化学工业   336篇
金属工艺   30篇
机械仪表   30篇
建筑科学   23篇
能源动力   79篇
轻工业   185篇
水利工程   4篇
石油天然气   6篇
无线电   128篇
一般工业技术   320篇
冶金工业   68篇
原子能技术   10篇
自动化技术   124篇
  2023年   52篇
  2022年   58篇
  2021年   87篇
  2020年   60篇
  2019年   72篇
  2018年   84篇
  2017年   70篇
  2016年   77篇
  2015年   42篇
  2014年   62篇
  2013年   98篇
  2012年   61篇
  2011年   80篇
  2010年   58篇
  2009年   46篇
  2008年   45篇
  2007年   36篇
  2006年   17篇
  2005年   16篇
  2004年   23篇
  2003年   15篇
  2002年   13篇
  2001年   11篇
  2000年   11篇
  1999年   6篇
  1998年   17篇
  1997年   17篇
  1996年   14篇
  1995年   9篇
  1994年   5篇
  1993年   10篇
  1992年   6篇
  1991年   4篇
  1990年   4篇
  1989年   6篇
  1988年   6篇
  1987年   2篇
  1986年   5篇
  1985年   11篇
  1984年   5篇
  1983年   8篇
  1982年   4篇
  1981年   8篇
  1980年   4篇
  1979年   4篇
  1976年   3篇
  1973年   1篇
  1971年   1篇
  1970年   2篇
  1968年   1篇
排序方式: 共有1359条查询结果,搜索用时 15 毫秒
1.
2.
Wireless Personal Communications - Recently, the theory of effective rate has attracted much attention, since it can take the delay aspect into account when performing channel capacity analysis. In...  相似文献   
3.
We report the mechanism involved in sol-gel auto-combustion synthesis of Ba–Sr-hexaferrite (Ba1-xSrxFe12O19; x = 0, 0.25, 0.5, 0.75 and 1, BSFO) ceramic powders through the analysis of the phases evolved during annealing of the as-synthesized powders, along with their structure and morphological studies. The XRD patterns of the as-synthesized samples indicate the formation of barium/strontium monoferrite ((Ba/Sr)Fe2O4) and maghemite (γ-Fe2O3) phases along with a minute amount of hematite (α-Fe2O3) phase. Annealing of these samples facilitates formation of BSFO phase through the solid state reaction between BaFe2O4 and γ-Fe2O3 phase. Interestingly, after annealing the samples with x = 0, 0.5 and 1, at 1000 °C for 2 h, we observed that phase pure Ba–Sr hexaferrite structure forms, but for samples with x = 0.25 and 0.75, high amount of hematite (α-Fe2O3) phase is observed, especially for x = 0.75. The reason associated with this could be the large difference between the ionic radii of Ba2+ and Sr2+ ions occupying the oxygen site. Furthermore, our study on annealing dependent phase evolution confirms that, this difference in ionic radii forbids the formation of a single phase Ba–Sr hexaferrite. The growth of clear hexagonal-shaped plate-like particles with varied particle sizes was observed for all the samples. The particle size variation may be due to the influence of the ionic radii difference on the sinterability of the samples. Our study provides a better understanding of synthesis mechanism of Ba–Sr hexaferrite samples.  相似文献   
4.
5.
6.
Multimedia Tools and Applications - In the way of communication, facial expression act as non-verbal communication and play an important role in social interaction by providing some contextual...  相似文献   
7.
Unlike nearly all engineered materials which contain bonds that weaken under load, biological materials contain “catch” bonds which are reinforced under load. Consequently, materials, such as the cell cytoskeleton, can adapt their mechanical properties in response to their state of internal, non-equilibrium (active) stress. However, how large-scale material properties vary with the distance from equilibrium is unknown, as are the relative roles of active stress and binding kinetics in establishing this distance. Through course-grained molecular dynamics simulations, the effect of breaking of detailed balance by catch bonds on the accumulation and dissipation of energy within a model of the actomyosin cytoskeleton is explored. It is found that the extent to which detailed balance is broken uniquely determines a large-scale fluid-solid transition with characteristic time-reversal symmetries. The transition depends critically on the strength of the catch bond, suggesting that active stress is necessary but insufficient to mount an adaptive mechanical response.  相似文献   
8.
Wireless Personal Communications - The paper reports the performance of an energy harvesting cognitive radio network under primary user emulation (PUE) attack. A secondary user (SU) can harvest...  相似文献   
9.
Russian Journal of Nondestructive Testing - Characterization of various industrial components without impairing their future utility increases the necessity of nondestructive testing (NDT)...  相似文献   
10.
In this study, we developed redox-sensitive vesicles using synthesised lipoyl cholesterol derivatives, a non-ionic surfactant and an optimum level of free cholesterol. Interestingly, concentration-dependent self-assembly was observed by scanning electron microscopy, wherein vesicles manifested as hollow spherical (at 0.15 mm ) and triangular (0.50 mm ). The redoxresponsive characteristics of the vesicles was probed in the presence of dithiothreitol; they underwent a clear increase in size as observed by dynamic light scattering measurements. These vesicles could easily encapsulate an anticancer drug, doxorubicin, and were observed to be stable in the presence of serum. They showed substantial release of the drug in response to biologically relevant stimulus, that is, glutathione. A toxicity assessment on HeLa and HepG2 cancer cells demonstrated activities of the drug-loaded vesicles comparable to that of free drug, whereas significantly enhanced toxicity and apoptotic induction were observed against drug-resistant HeLa cells, which was determined by studying the cellular internalisation of doxorubicin.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号